For Ludum Dare 22, Notch programmed a game in 48 hours called Minicraft. It's like a 2D minecraft.

Anyway the source is available (here: http://www.ludumdare.com/compo/ludum-dare-22/?action=preview&uid=398 ), and I was taking a look since I am interested in random generation of terrain and levels. In the code is a block of code which runs the core generation, and the algorithm to me seems familiar, but I can't put a name to it. I'd like to know exactly what it is so I can read more about it and learn how it works.